The GetDPI Photography Forum

Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!

Sean Reid's observations on M mount lenses on the G1

Jonas

Active member
OK Guy,

you gave us this list:

Checking the rest I did stop down more

5 1/125
6 1/250
7 1/60
8 1/250
9 1/200
10 1/500

Keep a eye on the light since it was in and out but after 4 i started stopping down which makes sense to me i usually try things wide open at first than start stopping down.
...and this image which I think is image 8 and taken with the lens stopped down quite a bit:

http://forum.getdpi.com/forum/attachment.php?attachmentid=12302&stc=1&d=1234704747

To me it is sharp in the center while being soft at the right border (trying to look at the focal plane which is a bit angled here). I see the same in a couple of the other images. Am I too critical or do we have a problem after all here?
 

Brian Mosley

New member
I'm wondering whether this is mainly to do with the angle of incidence of light on the outer edges of the frame with wide angle lenses... I haven't noticed a problem with my Hexanon lenses (57mm / 85mm / 135mm) or wide angle (and telecentric) 4/3rds lenses.

My recommendation for wide angle shooting on the G1 would be (apart from the slow lumix kit lens) the ZD 9-18 and ZD 11-22... both are telecentric designs and have no issues.

Kind Regards

Brian
 

Guy Mancuso

Administrator, Instructor
Well that right side is a little close to me so that one is not on the same plane as the focus which looks to me on the left rocks upper. The one with the log and red rock is dead on straight see if the right side is bad
 

Guy Mancuso

Administrator, Instructor
OK Guy,

you gave us this list:



...and this image which I think is image 8 and taken with the lens stopped down quite a bit:

http://forum.getdpi.com/forum/attachment.php?attachmentid=12302&stc=1&d=1234704747

To me it is sharp in the center while being soft at the right border (trying to look at the focal plane which is a bit angled here). I see the same in a couple of the other images. Am I too critical or do we have a problem after all here?

There could be a issue. Hard to tell without specifically shooting for that. Some look fine stopped down but we are dealing with DOF too and or lack of it on others.
 

Jonas

Active member
Guy: There could be a issue. Hard to tell without specifically shooting for that. Some look fine stopped down but we are dealing with DOF too and or lack of it on others.
Yes. Now I think I see this in image 7 and 8 as well (numbers wrong? the two ones preceeding the one we just talked about.

I agree that some more controlled testing is needed.
 

Jonas

Active member
My recommendation for wide angle shooting on the G1 would be (apart from the slow lumix kit lens) the ZD 9-18 and ZD 11-22... both are telecentric designs and have no issues.
Of these lenses the ZD9-18 is of interest to me. The samples at Imaging resource (@9mm) didn't impresse though - the corners are soft! Andthat with the lens stopped down to f/7 and f/8. I have also followed discussions at DPR about corner softness (with E-xx cameras).

Brian, are there other better samples available, perhaps taken with the G-1?
 

Guy Mancuso

Administrator, Instructor
Here is the WATE and pretty sure this was at 16mm setting shutter 1/320 and the corners look pretty good, not the same as the center but not far off either focus point is most likely dead center. Now the bottom is slighter closer to me also. Again wish i knew there may have been a issue i would have shot for it

The second one is at 1/640 with the WATE and looks like 5.6 and the corners look good. Trying to find images straight on which normally i never shoot
 

monza

Active member
Controlled testing is what is needed. It certainly doesn't hurt to look at existing photos; but it only gives part of the story.

I looked through perhaps 100 photos on flickr taken with many different M lenses last night, downloading the largest sizes and zooming in.

I was not able to find anything that was out of the ordinary, but before I reach a conclusion it would be helpful for those who have G1s and M lenses to do some controlled tests.

For that matter, I suppose it would be helpful to test everything, not just M lenses, but other adapted lenses. I have done so, and I have been unable to duplicate the issue.
 

monza

Active member
Regarding flickr, this Japanese gentleman has an impressive array of lenses. Here is a 35 'lux example, taken with the G1:

http://flickr.com/photos/yoshinori_kikuchi/3115557664/sizes/l/in/set-72157610940630628/

I went through over 100 of his photos, many of which are probably good tests as they have details of buildings, etc. all the way to the corners. There is one shot using a ZM 18/4 straight on to the wall of a building...exactly the sort of shot that would make corner 'smearing' quite obvious.

EDIT: Here is the ZM Distagon shot. Download the 'original' and zoom in. No smearing here...

http://flickr.com/photos/yoshinori_kikuchi/3127677298/sizes/l/in/set-72157610940630628/
 

Brian Mosley

New member
Of these lenses the ZD9-18 is of interest to me. The samples at Imaging resource (@9mm) didn't impresse though - the corners are soft! Andthat with the lens stopped down to f/7 and f/8. I have also followed discussions at DPR about corner softness (with E-xx cameras).

Brian, are there other better samples available, perhaps taken with the G-1?
I haven't checked the samples you're quoting here - I only have my own experience which shows the 9-18 being extremely sharp right into the corners. Unfortunately I'm not a professional tester so will be happy to wait for dpreview to prove me right :ROTFL:

Could be sample variation - or amateurish testing.

Kind Regards

Brian
 

peterv

New member
OK now I understand this is not a scientific test, etc, etc.
But it really shows quite well the effect that I'm trying to understand.

First is the D 25 Lux 100% A little to the left of the frame there's a leave I focussed on.
Second is the M 28 Cron. Same focuspoint.
Third is the D 25 Lux upper right corner.
Fourth is the M 28 Cron upper right corner.
Fifth there's the complete shot.

As you can see the Lux is sharper on the focuspoint.
Now the Lux' base aperture is at f1,4 and the Cron's is at f2.0, so as allways it's apples to oranges, in a way.
That said, the Lux is still sharper than the Cron @ f4,0.
The lens-camera communication and the firmware will probably help the Lux here.

It's the cornershot that I'm interested in.
This is the distortion I'd like to find out where it's coming from and what is causing it.
This is the distortion I talked about in my other examples.

We know about the following issues

- Maze Pattern in some raw converters
- CA when no post correction applied
- What else?

My question:
What causes the distortion we see in the corner of the upper right corner cron shot?

Thanks, Peter
 
R

Ranger 9

Guest
We know about the following issues

- Maze Pattern in some raw converters
- CA when no post correction applied
- What else?

My question:
What causes the distortion we see in the corner of the upper right corner cron shot?
I'm just guessing -- but again, that's all anyone can do, since the full Four Thirds spec is proprietary.

But based on the article I linked in a previous post, I'd say that:

-- Four Thirds lenses are designed to be "telecentric," i.e, designed so that rays from the lens strike the sensor at a fairly perpendicular angle. The angle at which rays strike the sensor is called the "chief ray angle."

-- The microlens array used in the Four Thirds sensor is optimized for the chief ray angle dictated by the lens spec.

-- Camera lenses that produce a significantly different chief ray angle will interact with the microlens array in a non-optimal way. Intuitively, I suspect that effects of this non-optimal interaction might include reduced sharpness, distortion, and color fringing.​

Those are the sorts of effects you're seeing, right?

This is kind of a new world for everybody. Until Four Thirds, digital-camera systems with interchangeable lenses were designed to work with legacy lens systems from the film era. That meant that microlenses etc. had to be compromises.

The effects of these compromises were hard to isolate, and often tended to be blamed on the lens -- e.g. the digicam website "lens tests" that would say "lens X has chromatic aberration" because they'd see color fringing... even when lens X had never shown any sign of chromatic aberration in years of use on film cameras. (Color fringing and chromatic aberration are NOT one and the same thing -- chromatic aberration is actually a specific lens design fault of which color fringing is only one possible symptom.)

With Four Thirds, for the first time, we started seeing cameras, lenses, and sensors that had been designed without any concessions to the film-camera world. It wasn't a big deal because relatively few people were using legacy lenses on Four Thirds cameras. Now Micro Four Thirds comes along, with its thinner body depth that makes it possible to adapt all kinds of crazy lenses, and we have to expect to see more dramatic effects from lens-design philosophies that conflict with the assumptions under which Micro Four Thirds sensors were designed.

Cripes, that sounds pedantic! But it seems clear that "your mileage may vary" is going to be more true than ever as we experiment with various lenses on Micro Four Thirds.
 

peterv

New member
Thanks! That's all very interesting and your explanation sounds logical to me.
And thanks for the link too. I read the article and thought it was very helpfull.

Maybe the rather naive assumption I (we) made was that we focussed too much on the mechanical aspects of this relatively new µFT phenomenon. Thinking that if we could fit a 20th century lens with an image circle that is wide enough (through an adapter) on a 21st century camera, everything would be just fine...

As I said above, we'll have to come up with a list of lenses (lens designs) that work well on the G1 and other µFT cameras

Kind Regards, Peter
 

Martin S

New member
I just conducted my own, totally unscientific test of the edge phenomena using a "film" lens on the G1 that is currently being discussed.

The lenses used were a 21 mm Leica ASPH, Olympus 25 mm pancake, and the 14-45 mm kit lens. I used a tripod, and self timer.

I used f 2,8, 4, and 8 on the Leica, f 2.8, 4 and 8 on the Olympus, and f 4.5, and 8 on the kit lens.

There was a small, but distinct zone of smearing, and light drop off in all 4 corners of the Leica images at f 2.8, a smaller zone at f 4, and no smearing at f8. All of the corners seemed to be equally involved.

The Olympus showed a much smaller zone of smearing, and light drop off at f 2.8, and none at all at f 4,and f 8. I guess this telecentric stuff works.

The kit lens, as expected, showed the least smearing, and light drop off in the corners at f 4.5, and none at f 8.

Again, I invite comments on this totally unscientific test.

Martin
 

Jonas

Active member
I haven't checked the samples you're quoting here - I only have my own experience which shows the 9-18 being extremely sharp right into the corners. Unfortunately I'm not a professional tester so will be happy to wait for dpreview to prove me right :ROTFL:

Could be sample variation - or amateurish testing.
Well, looking at the images it is hard to understand how the corners can be smeared due to an user error. But wth, maybe it is. Then *I* surely should stay away. You know I need a foolproof lens.

;)
 

scho

Well-known member
Here are some boring and quick wallpaper shots using the 18, 25, 35, and 50 mm Zeiss lenses. All shot with M8 and G1 at ISO 160 and 100 respectively. All at f/5.6 and about 4 feet from the wall. Center and upper left corner samples at 100%. Images imported into LR 2.2 and only levels adjusted, no sharpening applied and no corner corrections applied to the un-coded 18mm Distagon. All lenses had B+W 486 UV/IR filters on for both the M8 and G1 shots.
Bottom line, some corner distortion on all G1 shots except the 50mm. Keep in mind that these are flat field shots so unless you are doing flat copy work you may or may not notice the corner and side distortion, depending on subject matter, aperture, etc.

Images start here
 
I have read this whole thread and no one has pointed out that any M lens test is being done with a third party adapter, many of them of questionable precision. All it would take would be the slightest bit of tilt in the adapter to whack out the corners at 1.4.
 
R

Ranger 9

Guest
I have read this whole thread and no one has pointed out that any M lens test is being done with a third party adapter, many of them of questionable precision. All it would take would be the slightest bit of tilt in the adapter to whack out the corners at 1.4.
Agreed, but since there's no way to mount a third-party lens except via an adapter, it may be a moot point.

Thickness measurements of my CQ adapter vary by no more than 0.01mm around its periphery. If that's not good enough to get good corner performance, I don't think any third-party solution is going to give good corner performance.
 
Top